The Capitals’ main priority: protect their house. Washington assembled a phalanx in front of the net that the Bruins, save for a third-period Benoit Pouliot charge-and-shoot, could never break down. If the Bruins hope to solve their offensive woes, they can’t shrink in Washington’s house the way they did Saturday.

“You’ve got to battle for your space,’’ said Bruins coach Claude Julien. “It’s not there, you’ve got to find it. It doesn’t mean you’re going to have more. But you’re going to be in better position.

“The problem right now is that we’re not battling through those to get in the right position. The goaltender is seeing a lot, because their D’s are pushing us to the outside.

“We’re letting them do that to us. We’re not fighting through to make his view of the shot tougher.’’

When the Bruins are rolling, they turn defensive plays into counterattacks. The forwards drop back to help out. Once the Bruins gain possession, the forwards swing the other way with speed and hurtle over the blue line to establish their forecheck.

The Bruins couldn’t get their middle-of-the-ice legs whirring. The Capitals deployed a 1-4 trap to gum up center ice.

Once the Bruins gained the zone, most of their sniffs on Holtby came from the outside. The Capitals were happy to steer the Bruins to their wings and give them the perimeter. Their defensemen were stout in front of Holtby. They regularly dropped their weak-side wingers into the slot for support. The Capitals held a 27-8 advantage in blocked shots.

“Not much,’’ Pouliot said when asked how much room they’ve had in the house. “They play it pretty well. They keep us on the outside.’’

If there was one thing Julien didn’t like about his team in Game 2, it was the players’ competitive level in the crucial battles. He pointed to the breakdown on Nicklas Backstrom’s winning goal.

Patrice Bergeron won a defensive-zone draw against Backstrom. Bergeron pulled the puck back to Johnny Boychuk. With a hard rap, Boychuk aimed to clear the puck off the right wall. For some reason, Boychuk fanned on his clearing attempt.

Marcus Johansson, who had slipped off Andrew Ference’s check, chased down the puck and spotted Backstrom open at the left circle. Ference tried to recover and get in front of the shot, but Backstrom snapped his shot through Ference’s screen and into the net at 2:56.

It was a sweet strike for Backstrom, who had gotten a face full of Thomas’s blocker at 17:34 of the third period when he tried to whack at a covered puck.

Thomas didn’t see Backstrom’s release. He didn’t spot the puck until it was nearly on him. By then, it knuckled past the goalie, who made a quick sprint for the dressing room.

“The proof is the overtime goal,’’ Julien said. “We win the draw. They outmuscle us to the puck. They make a second effort to get a pass to the right area. They score a goal. We lost that battle and lost the game.’’

Thomas didn’t have to make many 10-alarm saves. His best stop came at 10:08 of the first overtime. It was one of those rare times the Capitals had some time and space in the offensive zone. Jay Beagle let an uncontested shot rip from the slot that Thomas gloved down.

But as thorough as the Bruins were in front of Thomas (37 saves), the Capitals were even better in front of Holtby (43 saves). Washington didn’t cheat defensively.

With Karl Alzner (31:11 of ice time) and John Carlson (31:21) leading the way, the Capitals smothered the Bruins and limited them to far too many one-and-done looks.

The only time Washington faltered was when Pouliot showed the will to bust through its formation and wipe out a 1-0 third-period deficit. Brian Rolston started the play with a shot on goal that glanced off Jeff Schultz. The puck was in no man’s land, out of reach for Holtby. Pouliot barreled through Washington’s protective layers and swiped the puck past Holtby at 12:13.

It was only Boston’s second goal of the series. Both have been scored by the third line of Pouliot and Rolston flanking Chris Kelly.

“Great effort to jump on that loose puck to tie the game and force it into overtime,’’ Julien said. “We need more of that from a lot of other players.’’

It was one of the few times the Bruins flexed their muscles and had pucks and people at the net. Washington has been too structured and disciplined to give up many other looks.

“At this stage of the year, you’d like to see more net-front traffic,’’ Julien said. “You’d like to see that puck going to the net a little bit more with guys heading in that direction.

“We don’t have a good enough commitment in that area right now to win hockey games.’’